Dynamo-electric machine



v. A. FYNN VSpt. 14,1926. 1,599,753

A DYNAMO ELECTRIC MACHINE l Filed Nov, 9, 1923 Patented Sept. 14, 1926.

UNITED STAT Es PATENT oEFlcE.

Application filed November 9, 19273.v Serial No. 673,685.

My invention relates more particularly` to polyphase motors and generators.

The accompanying diagrammatic draw-y ings show in Figure 1 one embodiment. of my invention, while Figure 2 shows the preferred form of rimary winding.

Referring to igure 1 which illustrates a two-'pole three-phase motor, both stationary and revolving members are kreierably .of the stator and rotor t pe and, t erefore, have no defined polar pro1ections. The figure shows a motor with -a revolving primary. The rotor carries a commuted winding 2 indicated by a heavy circle, connected to a commutator which is not'shown and with which co-operate brushes 9 andk 10, shown in the figure as resting directly on the winding 2. The rotor alsocarries a three-phase star connected winding 3, 4, 5, suitably interconnected with the commuted winding 2 and provided with slip-rings, 6, 7, 8 for connection to the sup ly. Figure ,2 illustrates this anangement rotor windings more clearly.

The stator of the motor carries a threephase arran ment of'windinffs 16, 18 and 19, of whic the first is disp aeed by less than 90 electrical -degrees from the brush axis and connected to the brushes with the interposition of the adjustable resistance l17, while the two others are displaced by 120 electrical degrees from cach other and from the first and are closed over the adjustable resistances 20 and 21. The axis of 16 is displaced from thebrush axis by the angle Va in a. direction opposed to that in which the rotor revolves. In addition to this an adjustable resistance 15 is connected to the brushes 9, 10 and is adapted to shunt the commutedy winding 2.

The operation'of the motor shown in Figure 1 is somewhat as follows: Assuming-the resistance 15 to be disconnected the resist'- ances 17, 2O and 2,1 are suitably adjusted and the slip-rings are connected to the supply, the motor starts like an ordinary polyphase induction motor. `The resistances in the stator circuits can be reduced ,in one or more steps to their normal value. The n'ormal value for 20 and 21 is zerothat vfor 17 is the one which gives the desired power' factor characteristic, this characteristic, is, however, also influenced by the magnitude of the angle a. Since the winding 16 is the only one which has an external impedance in circuit with it, a somewhat more balanced starting condition can be secured and the load on the brushes reduced by shunting the commuted Winding, -which forms the external impedance referred to, by means of the non-inductive resistance 15. At starting the voltage induced in the winding 16 is much greater than the onel induced in the commuted winding and 15 may `readily be given a value which will permit a considerable current to flow through it and 16 while the current through it and the commuted winding will be very much smaller. The commuted winding then carries two currents, one through it and the winding 16 and another through it and the resistance 15.and while these are not exactly opposed in phase, yet they neutralize each other in part.' In this way the starting may be improved and the load on the commutator reduced. As the sped increases the resistance 15 can be increased to infinity in one or more steps.

lVhen the machine closely approaches syn chronism the induction motor torque drops to a Very small value, but the winding 16 now develops a very powerful -synchronizing torque 1n conjunction with the revolving flux produced by the primary. Near synchronism this flux induces a.. very low voltage at slip frequency in .16 and a voltage of practically normal amplitude but slip frequency in the commuted winding. This brush voltage is preponderant near synchronism and because the frequency is very low the current it produces is practically in` phase with it. lVhen the primary flux is at right angles to therbrush axis, the brush voltage is at maximum as is also the current in 16 and, therefore, the smaller the angle a the greater the synchronizing torque. But 16 is not only to develop a synchronizing torque; it must also provide the'unidirectonal excitation and at least partly neutralize the armature reaction. -For these reasons. the winding 16 isfnot made to coincide with the brush axis or be displaced from it by 90 electrical degrees, but to oc cupy a position intermediatefbetween these two andone in which it will be'able to fulfill all three duties suliicientl well. Adisplacement of degrees or ess gives goed results with motors of average design.

After synchronism has been reached, the windings 18 and 19 become inactive, and ,the winding 16 contributes more or less to the unidirectional excitation or to the neutralization of the armature reaction as the load varies and in this way controls the power factor of the machine. The ampere when so doing, the winding 16 of Figure 1 turns of the winding 16 do not, however, will serve to control the terminal voltage.

vary proportionally with the load.

It is obvious that various changes may be V en a load is applied which is in excess made in details without departing from the of that which the machine can carry as a spirit of this invention; it is, therefore, to synchronous motor, it falls out of step but be understood that this invention isn'ot t0 continues to operateV as an asychronous,` be limited to the specific details shown und motor, `the windings 18 and 19 again coming described.

into action, until its final load limit is Having thus described the invention,what

reached. is claimed is:

When the primary is stationary the re- In-a dynamo electric machine, a. rimary volving flux revolves synchronouslyv with re-r and a secondary without defined po ar spect to it and the secondary revolves in the jections, a commuted and another win same direction as this revolving flux. In on the primary,ksaid other winding beingfffa synchronous operation the'speed of the adapted for connection to a polyphase sup` secondary is a littleshort of that of the re# ply, brushes carried by the secondary and col volvmg flux, at synchronismthe speed of operating with the commuted wind the secondary is the same as that o therethree windings on the seconder displaced volving flux. `In applying' this invention to by 120 electrical degrees, each ofysaid winda stationary primary, the brushes co-operatings forming part of an operatively closed ing with the commuted winding on the ricircuit and one of said windingsbeing conmary must revolve with the secondary, ut nected to said' brushes the 'operation of the machine will be as here that axis which is dis laced by 90 electrical exlsnlained for the converse arran ment. degrees fromvthe bru axis.

ince all motors are capabl `o ssigenerators, it will be clear that this mathis 5th day of November, 1923.

operating In testimony whereof I ax my signature f` chine will also be able to supply current and VALRE ALFREDFYN N l Certilieat'e of Correction.

y 'Itis hereb certified that in Letters Patent No. 1,599,753, granted september 14,-

1926,'1pon t e application of'Valre Alfred Fynn, of St. Louis, Missouri, for an improvement in Dynamo-Electric--Machines an error appears in the printed specification Vrequiring correction as follows: lsage 2, line 15 for a synchronous y read aeg/nehm; andthat the said Letters Patent should be withthisl:

ce. Signed and sealed this 26thy dayl of October, A.- D. 1926 [SEAL] Wma KINNAN,

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